shUla vratam is one of the eight maha vratam. The day when the Sun shines in the makara rAsi that is the thai(pushya) month new moon day is called the shUla vratam day. On that day the observer of the austerity should pray the Lord holding three headed spear (shUla) accompanied by Goddess sakti, after getting up. Then the worship of the God with anointment (abhishekam) and offerings (naivedyam) etc should be done with devotion. Then should worship in the abode of Lord siva. Donating to the devotees of Lord siva who wear rudrAxa beads should be done. Only one time meal should be taken along with the devotees.
Observing this shUla vratam would get one the victory over all the enemies, free from the terrific diseases, boon of having offspring and the prosperities. Finally the devotee would get the union in siva. By observing this vratam mahA vishNu killed the cruel daemon kAla nemi. parashu rAma killed kArta vIryArjuna after observing this vratam. mahA vishNu got rid of a worst head ache because of glory of this vratam. brahma got relieved from his highly painful stomach pain. The highly powerful Lord vIrabhadra(2) explained the greatness of this vratam to bhanu kambha